I am posting this story, which is a tech diving story, not in the cave diving forum but here. I am doing it because I think it illustrates a principle, which is that conservative planning may begin to seem onerous, but is always wise.
Peter and I have been cave diving for years. Shoot, we've been DIVING for years, all over the place and in all kind of conditions and at a wide variety of depths. We've taken a bunch of training to prepare to deal with emergencies, which we have basically never had. It's awfully tempting to stop observing the relatively limiting and annoying restrictions we were taught to respect.
On this particular dive, we were going into a cave new to us. Cave diving is always planned at the very least by the rule of thirds -- you never use more than 1/3 of your gas going in, so you have enough to get a buddy out, or more likely, to deal with anything which delays your exit. This cave, we were diving on double Aluminum 80s, so normally, we would have a 3000 psi fill, and plan to turn around and head home at 2000 psi. But because this cave was deep, we were bringing an additional tank, called a stage. Rules for stage usage vary, but we knew how much of the stage we would use, and how we would account for the needed reserves gas. This is all very simple once you are trained to do it, and we are very familiar with the process.
What was different in this cave was that the profile was going to tend deeper than we usually go. The really interesting and beautiful part of the cave was going to be down around 70 or 80 feet, which doesn't sound that deep until you realize we would have been running about45 minutes of depths averaging 60 feet before we ever got there. If you get out the tables, even an hour at 60 on 32% is a lot, and if from there, you head deeper, you are going to run out of no-deco time very quickly (and remember, everything we did going in, we have to do going out; so 45 minutes at 60 is really 90 if you exit).
So I had done the calculations for 10 minutes of backgas deco, and how much we needed to reserve to do that, and account for having to share gas while doing it, and we had planned our gas around those numbers. But when we got to the 70 foot section, it was SO beautiful . . . We both wanted to go on, and enjoy the cave a little more. Shoot, we weren't racking up that much deco, and we've never had a gas loss problem -- how bad could it be? But I am persistently paranoid, and we turned and headed back.
We picked up our stages and started breathing them, and everything was fine. Shoot, we could have gone a bit further . . . except I see some weird light signals from behind me, and turn around, and Peter is wreathed in bubbles. It looks like his stage reg has exploded, but once he turns it off, it's clear the issue is that a hose has come somewhat unscrewed from the first stage. He shuts the tank off, switches to the regulators attached to the tanks on his back (where he has tons of gas) and once the hose is depressurized, he is able to screw it back in until it doesn't leak. Total gas loss is 100 psi; we have plenty to do the deco we have incurred.
What would have happened if we had gone further? What would have happened if he had not been able to handle the malfunction so neatly?
Lessons learned: Plans are conservative for a reason. Problems you haven't had are only that -- they are not problems you can't, or are never going to have. Gas is time, and sometimes you need time.
During our 10 minutes of deco, I had a lot of time to reflect on how much I owe to the people who taught me to be careful.
Peter and I have been cave diving for years. Shoot, we've been DIVING for years, all over the place and in all kind of conditions and at a wide variety of depths. We've taken a bunch of training to prepare to deal with emergencies, which we have basically never had. It's awfully tempting to stop observing the relatively limiting and annoying restrictions we were taught to respect.
On this particular dive, we were going into a cave new to us. Cave diving is always planned at the very least by the rule of thirds -- you never use more than 1/3 of your gas going in, so you have enough to get a buddy out, or more likely, to deal with anything which delays your exit. This cave, we were diving on double Aluminum 80s, so normally, we would have a 3000 psi fill, and plan to turn around and head home at 2000 psi. But because this cave was deep, we were bringing an additional tank, called a stage. Rules for stage usage vary, but we knew how much of the stage we would use, and how we would account for the needed reserves gas. This is all very simple once you are trained to do it, and we are very familiar with the process.
What was different in this cave was that the profile was going to tend deeper than we usually go. The really interesting and beautiful part of the cave was going to be down around 70 or 80 feet, which doesn't sound that deep until you realize we would have been running about45 minutes of depths averaging 60 feet before we ever got there. If you get out the tables, even an hour at 60 on 32% is a lot, and if from there, you head deeper, you are going to run out of no-deco time very quickly (and remember, everything we did going in, we have to do going out; so 45 minutes at 60 is really 90 if you exit).
So I had done the calculations for 10 minutes of backgas deco, and how much we needed to reserve to do that, and account for having to share gas while doing it, and we had planned our gas around those numbers. But when we got to the 70 foot section, it was SO beautiful . . . We both wanted to go on, and enjoy the cave a little more. Shoot, we weren't racking up that much deco, and we've never had a gas loss problem -- how bad could it be? But I am persistently paranoid, and we turned and headed back.
We picked up our stages and started breathing them, and everything was fine. Shoot, we could have gone a bit further . . . except I see some weird light signals from behind me, and turn around, and Peter is wreathed in bubbles. It looks like his stage reg has exploded, but once he turns it off, it's clear the issue is that a hose has come somewhat unscrewed from the first stage. He shuts the tank off, switches to the regulators attached to the tanks on his back (where he has tons of gas) and once the hose is depressurized, he is able to screw it back in until it doesn't leak. Total gas loss is 100 psi; we have plenty to do the deco we have incurred.
What would have happened if we had gone further? What would have happened if he had not been able to handle the malfunction so neatly?
Lessons learned: Plans are conservative for a reason. Problems you haven't had are only that -- they are not problems you can't, or are never going to have. Gas is time, and sometimes you need time.
During our 10 minutes of deco, I had a lot of time to reflect on how much I owe to the people who taught me to be careful.
